Whereas in aquatic ecosystems the effects of introduced predators on prey populations were frequently studied, less is known about the interactions between predators. We performed a whole-lake experiment by stocking a non-native top-predator (pikeperch) to two residential piscivores (perch and pike). Annual consumption by the piscivores increased 1.7 times after stocking, attributable to the stocked pikeperch and increased pike abundances. Furthermore, all piscivores increasingly fed on small perch. The forced habitat shift of piscivorous perch in combination with increased predation on small perch led to a decreased abundance of large perch, attributable to the compensatory effects of intraguild predation and cannibalism.